This invention relates to a track type vehicle undercarriage.
In the undercarriage of the kind specified, a track link chain extends round an idler and a sprocket mounted, respectively, on the front and rear parts of a track frame, and the track link chain is provided with track rollers adapted to roll along rails located in the lower part of the track frame, and further a semi-circular front rail is installed in the vicinity of the idler.
In such a construction, however, when the rollers ride on the front rail shock noise will occur causing a problem with noise, and also when the rollers move rearwardly so as to mesh with the sprocket, the rollers will strike against the bottom of the teeth of the sprocket thereby generating a loud shock noise.
In order to solve this problem, there has been proposed a system wherein upper rails extend round the sprocket and the idler to prevent the rollers from striking against the sprocket.
However, this construction is disadvantageous in that when the rollers roll along the upper rails the rotary resistance becomes larger than the roller turning force with the result that the rollers will slidably move along the upper rails thus causing early wear of both the rollers and upper rails so as to reduce the durability thereof, and also because the rollers continue to rotate when they pass through the upper rails, the service life of the rotating support parts of the rollers, in particular, the floating seals will be reduced.